In a Paper entitled "Gas Turbine Key to solid waste disposal" by Bert Goldrath published by Ruston Gas Turbines Limited of Lincoln England, there is described a gas turbine which is driven by hot, gaseous products of combustion produced in a fluidised bed to which combustible solid material and air are supplied. The fluidised bed is contained in a cylindrical combustor 22 ft. high and 91/2 ft. in diameter. The bed lies at the bottom of this cylinder and has a depth of 2 ft. The size of the fluidised bed combustor renders this equipment unsuitable for many applications.